Docile and shy, the deer seems like one of nature’s gentlest animals, programmed to choose flight over fight. But once a year, male stags turn aggressive. During mating season, or “rut,” the stag’s hormones take over, turning the normally-calm animals into fighting machines, willing to fight to the death to prove their dominance.

Tonight, Do Or Dietackles a life-or-death scenario when an unsuspecting tourist catches the eye of a stag in heat. During mating season, spectators should never get too close to a rutting stag, and coming between a stag and his female could prove fatal. So once the beast realizes the tourist isn’t a potential mate, things turn violent as the stag begins his charge.

During rut, stags emit a deep, bellowing roar to assert themselves against their enemy, using their sharp antlers and powerful kicks to attack. Fighting back against a rutting stag is not an option. And with an average running speed of over 70 miles per hour – three times as fast as most humans can sprint – a stag can easily chase down a human that crosses his path.